Technical grade monoammonium phosphate is primarily produced by the reaction of furnace grade phosphoric acid with ammonia. However, furnace grade acid is very expensive and is expected to continually increase in price. Therefore, a need exists to provide a purified monoammonium phosphate which can be prepared from less expensive starting materials, but which will nevertheless be usable in applications heretofore requiring "technical grade" monoammonium phosphate.
In the past, attempts to prepare relatively pure monoammonium phosphate from less pure "wet process" acid have not been economically attractive because impurities that are present in wet process grade phosphoric acid, upon ammoniation of the acid, precipitate in a form which is very difficult to remove. It is necessary to remove these impurities from the ammoniated phosphoric acid so that a relatively pure monoammonium phosphate product can be produced.
Therefore, an unsatisfied need exists for the production of monoammonium phosphate from wet process grades of phosphoric acid, which method would also allow for efficient and simple removal of the associated impurities by the use of conventional equipment and techniques. Further, a need has arisen for a process for the production of ammonium phosphate from wet process phosphoric acid and ammonia that provides for efficient removal of precipitated impurities from the ammoniated phosphoric acid solution and produces a relatively pure monoammonium phosphate.